Selection of phenyl hydrazine derivatives as an Sn4+ reductant for tin-lead perovskite solar cells

Hydrazine derivatives have been extensively studied as some of the earliest reductants for Sn-Pb mixed perovskite precursors. However, phenyl hydrazine (BH) as a strong reductant for Sn-based perovskite solutions has not been reported yet, and Sn2+ is unusually oxidized in the precursor solution with BH additives in our experiment. Thus, not all organic reductants are suitable as additives, and therefore selecting a suitable reductant should be paid special attention to. Herein, it is found that BH as a Br & oslash;nsted base deprotonates MA(+) to produce HI, which further catalyzes the oxidation of Sn2+ by DMSO. As an alternative, hydrochloride phenyl hydrazine with a sulfonic amide group (-SO2-NH2) is added to the precursor as a reductant and passivator. As a result, a power conversion efficiency of 22.01% is achieved, and prolonged shelf stability is realized.